1. Field of the Invention
The present invention relates generally to train control and braking systems, and in particular to braking systems and methods of determining dynamic braking data and information for use in a braking model or algorithm on an operating train.
2. Description of the Related Art
As is known in the art, trains, which include at least one locomotive and, typically, multiple railcars, employ complex braking systems and arrangements for slowing or stopping the train in variety of conditions and environments. For example, existing braking systems are shown and described in U.S. Publication No. 2007/0142984 and U.S. Pat. Nos. 8,019,496; 6,314,358; 5,744,707; 4,562,543; 4,384,695; 4,235,402; 4,005,838; 4,005,837; 3,921,946; and 3,731,193. Further, many train systems and networks use some form of computer-controlled train management system, such as a Positive Train Control (PTC) system (e.g., the I-ETMS® of Wabtec Corporation). These computer-controlled train management systems have on-board computers or controllers that are used to implement certain train control and management actions for ensuring safe and effective operation of the train.
In addition, the computerized braking control system of the train management system uses a braking model or algorithm to build or determine stopping distances as the train advances or travels through the train network. Such stopping distances are based upon certain specified train-based operating parameters and/or variable feedback from a number of sensor systems and/or ancillary measurements or determinations, e.g., track grade, track curvature, train speed, train weight, brake pipe pressure, braking system reservoir pressures, and the like. Accordingly, the braking model must account for those various parameters, but must also account for variation in the system parameters while providing a stopping distance that has a very low probability of stopping the train past the target location.
As is also known, these stopping distances are used to build a braking profile or curve that estimates or predicts when train will stop, such as at a specified target point or area that is positioned ahead on the track. This braking profile is continually calculated using the braking model and using the changing feedback and variable determinations to provide an updated braking profile or curve ahead of the train. In general, this braking profile or curve visually illustrates to the train operator where the train is predicted to stop if a full-service penalty brake application is initiated. Again, this braking profile or curve is continually (e.g., 1-3 times per second) updated so that the operator has an ongoing understanding of how and when the train would stop during a penalty brake situation.
The braking model or algorithm is initially developed by executing a multitude of scenarios under a wide variety of conditions and states related to all aspects of the train and its projected surrounding environment. Further, and based upon certain rules and/or standards, a safety factor is determined to ensure to a specified probability that the required stopping distance will be safely short of the target. Still further, and during a penalty brake application, the braking model continues to monitor and predict the stopping distance to the specified target location. While a prediction that the train will stop before or at the target location may not pose a significant safety issue, a predicted stop after the target location could prove problematic or unsafe.
In order to provide additional braking capacity and functionality, many trains are equipped with a Dynamic Brake System, which uses the traction motors of a railroad vehicle as generators during the braking process. Specifically, such a Dynamic Brake System provides additional braking force for the train by turning the motors that drive the wheels into generators and transferring the energy into resistors. In the past, and as discussed, the PTC braking model or algorithm has been developed to safely predict the stopping distance and characteristics of a train so that the PTC system can prevent the train from exceeding any speed restrictions or authority limitations. Through years of development, this braking model or algorithm has been refined to achieve accurate results within the requirements for safe operation.
However, one force that has never been properly accounted for is the total dynamic braking forces produced by the locomotive consist. The dynamic braking force has been excluded primarily based on guidance from the Federal Railroad Administration (FRA) and their belief that it could not be safely accounted for or relied upon. The drawback for the railroad operators is that by excluding dynamic braking force, the PTC system becomes too conservative, and may slow down overall throughput on the railroad due to excessive warnings and/or unnecessary enforcements. Therefore, accounting for dynamic braking force in the PTC braking model or algorithm has the potential to improve rail network throughput and reduce nuisance warning and enforcement events to crews that are properly handling their train.